This invention relates to an aircraft fuel tank construction and more particularly to construction of a fuel tank which is assembled from a cylindrical center section, a conical nose section and a conical tail section, and which is disassembled during shipment and storage.
For military purposes, it is desirable to manufacture lightweight refueling tanks in sections which can be nested during shipment and storage for maximum storage capacity but so constructed that they can be quickly and easily assembled in securely connected, fully sealed, liquid tight relationship. To enable the center section, and center sections of other such tanks, to be nested one within the other and thus form a compact package, the center section is formed with a longitudinal gap throughout its length. The side walls of the section facing the gap are connected together and the gap sealed when the center section is assembled with the two end sections. The end sections are sealed at their juncture with the center section by a circumferential end seal, which is also in sealing contact with the seal for the center section. Such a tank construction is described in U.S. Pat. No. 2,876,923.
There are several problems associated with known tank constructions. In some tank constructions, the center section is joined by fasteners and the width of the gap is not fixed but dependent on the degree to which the fasteners are tightened. With this type of construction, the center section seal may either be overcompressedor undercompressed by improperly torquing the fasteners, which may make the seal ineffective. Another problem is that overtorquing the fasteners by unskilled personnel may cause the center section seal to elongate and resultingly compress the end seals at their interface with the center section seal, thereby resulting in a fuel leakage path at this point. Similarly, contraction or expansion of the center section seal due to temperature changes may also cause the tank to leak at the interface of the seals because of the relative movement between the seals.
Another problem associated with known fuel tanks is that often the center section seal cannot be visually inspected after the seal is seated. As a consequence, an improperly seated seal cannot be detected until the fuel tank is filled with fuel and a leak occurs.
Another problem of known fuel tanks is that one or more of the joints of the fuel tank may protrude above the surface of the tank causing an increase in aerodynamic drag.